Base of Principal Aquifer for Parts of the North Platte, South Platte, and Twin Platte Natural Resources District, Western Nebraska

By

Christopher M. Hobza, Jared D. Abraham, James C. Cannia, Michaela R. Johnson, and Steven S. Sibray

104° 103° 102° 101°

42°

41°

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Base from National Atlas of the United States, 2014

Lambert Conformal Conic projection

Horizontal coordinate information is referenced to the 

North American Horizontal of 1983 (NAD 83)

South Platte Natural Resources District (NRD)

 airborne electromagnetic area

Twin Platte NRD airborne electromagnetic area

North Platte NRD airborne electromagnetic area

Test hole 

2010 airborne electromagnetic flight line

2008 and 2009 airborne electromagnetic flight line 

(Abraham and others, 2012)

EXPLANATION North Platte Natural 

Resources District

South Platte Natural 

Resources District

Twin Platte Natural 

Resources District

Cooperative Hydrology 

Study boundary

Index map

Shaded relief from Esri, 2013

Figure 1.  Location of 2010 airborne electromagnetic (AEM) flight lines (this study), and 2008 and 2009 airborne electromagnetic flight lines.

ABSTRACT

Water resources in the North and South Platte River valleys of

Nebraska, including the valley of Lodgepole Creek, are critical to the

social and economic health of the area, and for the recovery of threatened and endangered species in the Platte River Basin. Groundwater

and surface water are heavily used resources, and uses are regulated

in the study area. Irrigation is the dominant water use and, in most

instances, is supplied by both groundwater and surface-water sources.

The U.S. Geological Survey and its partners have collaborated to use

airborne geophysical surveys for areas of the North and South Platte

River valleys including the valley of Lodgepole Creek in western

Nebraska. The objective of the surveys was to map the aquifers and

underlying bedrock topography of selected areas to help improve

the understanding of groundwater–surface-water relations to guide

water-management decisions. This project was a cooperative study

involving the North Platte Natural Resources District, the South

Platte Natural Resources District, the Twin Platte Natural Resources

District, the Conservation and Survey Division of the University of

Nebraska-Lincoln, and the Nebraska Environmental Trust.

This report presents the interpreted base-of-aquifer surface for

part of the area consisting of the North Platte Natural Resources District, the South Platte Natural Resources District, and the Twin Platte

Natural Resources District. The interpretations presented herein build

on work done by previous researchers from 2008 to 2009 by incorporating additional airborne electromagnetic survey data collected in

2010 and additional test holes from separate, related studies. To make

the airborne electromagnetic data useful, numerical inversion was

used to convert the measured data into a depth-dependent subsurface

resistivity model. An interpretation of the elevation and configuration

of the base of aquifer was completed in a geographic information system that provided x, y, and z coordinates. The process of interpretation

involved manually picking locations (base-of-aquifer elevations) on

the displayed airborne electromagnetic-derived resistivity profile by

the project geophysicist, hydrologist, and geologist. These locations,

or picks, of the base-of-aquifer elevation (typically the top of the

Brule Formation of the White River Group) were then stored in a georeferenced database. The pick was made by comparing the inverted

airborne electromagnetic-derived resistivity profile to the lithologic

descriptions and borehole geophysical logs from nearby test holes.

The database of interpretive picks of the base-of-aquifer elevation was

used to create primary input for interpolating the new base-of-aquifer

contours.

The automatically generated contours were manually adjusted

based on the interpreted location of paleovalleys eroded into the

base-of-aquifer surface and associated bedrock highs, many of which

were unmapped before this study. When contours are overlain by

the water-table surface, the saturated thickness of the aquifer can be

computed, which allows an estimate of total water in storage. The

contours of the base-of-aquifer surface presented in this report may

be used as the lower boundary layer in existing and future groundwater-flow models. The integration of geophysical data into the contouring process facilitated a more continuous and spatially comprehensive

view of the hydrogeologic framework.

INTRODUCTION

Water resources in the North and South Platte River valleys

of Nebraska, including the valley of Lodgepole Creek (fig. 1), are

critical to the social and economic health of the area, and the management of endangered species along the Platte River corridor. Both

groundwater and surface water are heavily used resources, and uses

are regulated in the study area and in the entire Platte River Basin. In

addition to regulated water resources use is the need to provide water

for the recovery of threatened and endangered species in the Platte

River Basin. The Platte River Recovery and Implementation Program

(PRRIP) is a partnership between the U.S. Department of the Interior,

and the States of Wyoming, Colorado, and Nebraska to manage habitat and water for recovery of the threatened and endangered species

in the Big Bend reach (not shown in any maps) of the Platte River

(Kenny, 2008). Water for the program is stored in Lake McConaughy

or received from the South Platte River (fig. 1). Some of the water

from the North Platte River is distributed downstream to the Big Bend

reach of the Platte River to improve and maintain the habitat of threatened or endangered species (Kenny, 2008). Before reaching Lake

McConaughy (fig. 1), the lowest reservoir on the North Platte River,

snowmelt runoff from its mountain headwaters passes through many

reservoirs, canal systems, and tributaries, and provides a large percentage of the recharge to the aquifers within the valley alluvium. The

complexities of the interaction of the groundwater and surface-water

systems are similar in the South Platte River Basin. Understanding the

complex groundwater and surface-water interactions of the North and

South Platte Rivers, and Lodgepole Creek (fig. 1), allows managers

to better regulate the limited supplies of water for all uses including

environmental flows required for endangered species.

Primary groundwater and surface-water management concerns

include those related to water availability and water quality for human

uses, and these concerns exist both locally and downstream from

the study area. Irrigation is the dominant water use, which in most

instances is supplied by both groundwater and surface-water sources

(Carney, 2008; Luckey and Cannia, 2006). The study area covers

parts of western Nebraska, and typically receives between 33 and

48 centimeters (cm; 13 and 19 inches [in.], respectively) of precipitation annually (National Oceanic and Atmospheric Administration,

2014). Supplemental water through irrigation is necessary for agriculture. In the South Platte River and Lodgepole Creek drainage basins,

dual sources (both groundwater and surface water) are used to irrigate

approximately 54,000 hectares (ha; 133,000 acres) of crops (South

Platte Natural Resources District, 2008). Much of the water provided for irrigation is used and reused multiple times along its course

downstream. The use of dual-sources creates a complex interaction

between its source and its fate, which can make water management

challenging.

Because of the multiple water uses and the consequential management challenges, additional data regarding water resources are

required for use in other studies, including the U.S. Geological Survey (USGS) High Plains “Groundwater Availability Study” (Houston and others, 2013; Qi, 2010; Qi and Christenson, 2010; Stanton

and others, 2011) and the Cooperative Hydrology Study (COHYST;

Carney, 2008; Peterson, 2007; Luckey and Cannia, 2006). Additionally, water-resources data are actively being incorporated within the

“Simulation of Groundwater Flow and Analysis of the Effects of the

Water Management Options in the North Platte Natural Resources

District (NPNRD) Study,” which will be referred to hereinafter as

the NPNRD Groundwater Management Model (S.M. Peterson, U.S.

Geological Survey, oral commun., 2011). Refinement of the base-ofaquifer (BOA) configuration will improve the reliability of the predictions made with these models. One approach to deriving and refining

the BOA configuration is the use of airborne electromagnetic (AEM)

surveys.

From 2008 to 2010, the USGS and its cooperators collaborated

to use airborne geophysical surveys for areas of the North and South

Platte River valleys including the valley of Lodgepole Creek in

western Nebraska (fig. 1). The objective of the surveys was to map

the aquifers and underlying bedrock topography of selected areas to

help improve the understanding of groundwater and surface-water

interactions to guide water-management decisions. This project was

a cooperative study involving the Nebraska Environmental Trust,

the NPNRD, the South Platte Natural Resources District (SPNRD),

the Twin Platte Natural Resources District (TPNRD), Conservation

and Survey Division of the University of Nebraska-Lincoln, and the

USGS.

This report presents the interpreted BOA surface for parts of the

area consisting of the NPNRD, SPNRD, and TPNRD (figs. 2 and 3).

The interpretations presented in this report build on previous work

(Abraham and others, 2012) by including AEM survey data collected

in 2010 (U.S. Geological Survey Crustal Geophysics and Geochemistry Science Center, 2014), and lithologic descriptions and borehole

geophysical logs from additional test holes provided by separate

but related studies (James C. Cannia, U.S Geological Survey, written commun., 2012; Hobza and Sibray, 2014; T.A. Kuntz, Adaptive

Resources Inc., written commun., 2012). This information will be

used to improve the accuracy and representativeness of the existing

hydrogeologic frameworks of the NPNRD, SPNRD, and TPNRD.

The geology and water resources in the study area have been

described by many earlier investigators (Darton, 1903a, 1903b; Wenzel and others, 1946; Bjorklund, 1957; Smith, 1969; Smith and Souders, 1971, 1975; Swinehart and others, 1985; Souders, 1986; Sibray

and Zhang, 1994; Steele and others, 2007). Cannia and others (2006)

constructed a hydrostratigraphic framework and characterization of

underlying aquifers of the COHYST area (fig. 1) that were used in

recently published groundwater-flow models (Carney, 2008; Luckey

and Cannia, 2006), which included all of the study area. Within the

study area the principal aquifer is the High Plains aquifer system,

which is composed of the following geologic units:

• Quaternary-age deposits of alluvium and valley-fill deposits,

and eolian sand;

• Broadwater Formation of Tertiary age;

• Ogallala Group of Tertiary age;

• Arikaree Group of Tertiary age; and

• Brule Formation of the White River Group (referred to hereafter as the Brule) of Tertiary age, where the Brule is fractured

(Gutentag and others, 1984; Cannia and others, 2006).

The Brule forms the BOA in most parts of the study area. Cannia

and others (2006) mapped localized areas where the Brule is absent;

undifferentiated Cretaceous-age units form the BOA near the North

Platte River in the western part of the NPNRD and in the TPNRD

south of Lake McConaughy (fig. 1).

METHODS

This section of the report summarizes the methods used to

enhance existing BOA contours using information from additional

AEM surveys. Further detail and information regarding the processing workflow including geophysical data processing and inversion

can be located in Abraham and others (2012).

Hypsometric contours of the BOA surface of the study area were

modified using the following data: lithologic descriptions and borehole geophysical logs from additional test holes, time-domain electromagnetic (TDEM) surveys, and AEM surveys. Investigation of the

BOA began by first assembling all the available information, which

included existing geographic information system (GIS) data for BOA

contours (Abraham and others, 2012; Cannia and others, 2006),

depth to the geologic units that form the BOA at available test holes

(University of Nebraska-Lincoln, Conservation and Survey Division,

2014), test holes drilled in separate but related studies (J.C. Cannia,

U.S. Geological Survey, written commun., 2012; Hobza and Sibray,

2014; T.A. Kuntz, Adaptive Resources Inc., written commun., 2012),

and digitized unpublished hand-drawn outcrop maps (R.F. Diffendal Jr., University of Nebraska-Lincoln, Conservation and Survey

Division, unpub. data, 2013; J.B. Swinehart, University of Nebraska-Lincoln, Conservation and Survey Division, unpub. data, 2013).

The data supporting the BOA interpretations presented in this report

include information from AEM surveys completed in 2010 using

the SkyTEM system (U.S. Geological Survey Crustal Geophysics

and Geochemistry Science Center, 2014). AEM surveys increasingly

have been used to characterize aquifers and their geologic setting

(Smith and others, 2007). The SkyTEM is a TDEM mapping platform that was used to map the electrical properties of earth materials

from the near-surface 10 meters (m; 33 feet [ft]) down to depths of

300–400 m (984–1,312 ft; U.S. Geological Survey Crustal Geophysics and Geochemistry Science Center, 2014).

For the 2010 AEM surveys, approximately 1,890 linear kilometers (km; 1,174 miles [mi]) of data were collected (fig. 1). The AEM

surveys for the selected areas were conducted using two distinct

methods: block flights and reconnaissance lines. Block flights

were characterized by tightly spaced lines, uniformly spaced 220–

400 m (722–1,312 ft) apart, and trended in a uniform direction. An

example of a block flight oriented in a north-south direction can be

located northwest of Sidney in figure 1. The second configuration

used widely spaced lines oriented in the direction likely to provide

the widest areal coverage possible for identifying the BOA. These

widely spaced lines were termed reconnaissance lines and provided

an initial view of the subsurface in areas where the existing geologic

framework was poorly constrained. An example of a reconnaissance

line can be located as the single flight line trending north-south and

beginning northeast of Sidney in figure 1. Within the NPNRD, 2010

AEM data collection included two block flights: one west of Bayard

and another east of Bridgeport (fig. 1). Several reconnaissance lines

also were collected parallel to the North Platte River, and several

lines oriented north-south, east of Bridgeport (fig. 1). Within the

SPNRD, two large block flights trending north-south were collected

north of Lodgepole Creek: one in western Cheyenne County and

one extending north from northwest of Sidney into the NPNRD

was collected (fig. 1). Reconnaissance lines also were collected

near the block flights (fig. 1). Within the TPNRD, AEM data collection included the following two block flights: one along Western

Canal near the South Platte River, extending into Deuel County, and

another along the North Platte River downstream from Lake McConaughy (fig. 1). Two reconnaissance lines were collected north of the

block flight near Lake McConaughy (fig. 1). Three additional test

holes were drilled in Keith County to provide additional ground truth

for interpreting the reconnaissance lines (James Cannia, U.S. Geological Survey, written commun., 2012; fig. 1).

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Base from National Atlas of the United States, 2014

Universal Transverse Mercator projection, zone 13 north, in meters

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83)

National Geodetic Vertical Datum of 1929 (NGVD 29)

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EXPLANATION

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4400–4,450, 4,650–4,700, 4,900–4,950, 5,150–5,200

3,200–3,250, 3,450–3,500, 3,700–3,750, 3,950–4,000, 4,200 –4,250, 

4,450–4,500, 4,700–4,750, 4,950–5,000, 5,200–5,250

3,250–3,300, 3,500–3,550, 3,750–3,800, 4,000–4,050, 4,250–4,300, 

4,500–4,550, 4,750–4,800, 5,000–5,050, 5,250–5,300

3,300–3,350, 3,550–3,600, 3,800–3,850, 4,050–4,100, 4,300–4,350, 

4,550–4,600, 4,800–4,850, 5,050–5,100, 5,300–5,350

North Platte Natural Resources District airborne electromagnetic survey boundary 

South Platte Natural Resources District airborne electromagnetic survey boundary

Structure contour—Shows altitude of base of aquifer. Dashed 

where approximately located. Contour interval is 50 feet. Datum 

is National Geodetic Vertical Datum of 1929 (NGVD 29)

Structure contour control point—Symbol color indicates elevation 

range, in feet above NGVD 29

17 et uoR et atS

Lisco

Creek

Tributary of

Tributary of Bayard Drain

Creek

Creek

Creek

Figure 2.  Elevation of the base-of-aquifer surface for parts of the North Platte Natural Resources District and the South Platte Natural Resources District, 2014.

U.S. Department of the Interior

U.S. Geological Survey

 Scientific Investigations Map 3310

Sheet 1 of 2

Prepared in cooperation with the 

North Platte Natural Resources District, South Platte Natural Resources District, Twin Platte Natural Resources District, Conservation and Survey Division of the University of Nebraska-Lincoln, and the Nebraska Environmental Trust

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not 

imply endorsement by the U.S. Government.

This map was printed on an electronic plotter directly from digital files. Dimensional calibration may vary 

between electronic plotters and between X and Y directions on the same plotter, and paper may change 

size due to atmospheric conditions; therefore, scale and proportions may not be true on plots of this map.

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment—visit http://www.usgs.gov or call 1–888–ASK–USGS 

This report is available at http://dx.doi.org/10.3133/sim3310.

Suggested Citation: Hobza, C.M., Abraham, J.D., Cannia, J.C., Johnson, M.R., and Sibray, S.S., 2014, Base 

of principal aquifer for parts of the North Platte, South Platte, and Twin Platte Natural Resources Districts, 

western Nebraska: U.S. Geological Survey Scientific Investigations Map 3310, 2 sheets, http://dx.doi.

org/10.3133/sim3310. ISSN 2329-132X (online)